Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current Assets:
Cash and cash equivalents	$ 1,637	$ 4,054
Marketable securities	605	1,361
Notes receivable - current	1,795	1,750
Prepaid and other current assets	683	668
Total Current Assets	4,720	7,833
Property, plant and equipment, at cost:
Property, plant and equipment	101,146	101,187
Less accumulated depreciation, depletion and impairment	(65,771)	(65,778)
Net property, plant and equipment	35,375	35,409
Restricted cash	3,668	3,668
Notes receivable - non-current	2,548	3,328
Total Assets	46,311	50,238
Current Liabilities:
Accounts payable	1,000	538
Accrued liabilities	1,595	2,352
Current portion of asset retirement obligations	936	1,078
Total Current Liabilities	3,531	3,968
Asset retirement obligations, net of current portion	4,787	4,653
Other long-term liabilities and deferred credits	500	500
Total Liabilities	8,818	9,121
Commitments and Contingencies
Stockholders' Equity:
Common stock, 100,000,000 shares authorized, $.001 par value; Issued shares - 28,831,409 and 27,790,324, respectively Outstanding shares - 28,823,384 and 27,782,299, respectively	29	28
Paid-in capital	297,981	297,250
Accumulated other comprehensive (loss) income	(650)	287
Accumulated deficit	(259,609)	(256,190)
Treasury stock (8,025 and 8,025 shares, respectively), at cost	(258)	(258)
Total Stockholders' Equity	37,493	41,117
Total Liabilities and Stockholders' Equity	$ 46,311	$ 50,238

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).